1. Field of the Invention
The present invention involves annuloplasty devices and delivery devices for the annuloplasty devices that are used for treating a medical condition such as a defective mitral valve.
2. Discussion of Related Art
FIG. 1A illustrates a heart 10. There are four valves in the heart 10 that serve to direct the flow of blood through the two sides of the heart 10 in a forward direction. The four valves are a mitral valve 20, an aortic valve 18, a tricuspid valve 60, and a pulmonary valve 62 as illustrated in FIG. 1A. The mitral valve 20 is located between the left atrium 12 and the left ventricle 14. The aortic valve 18 is located between the left ventricle 14 and the aorta 16. These two valves direct oxygenated blood coming from the lungs, through the left side of the heart, into the aorta 16 for distribution to the body. The tricuspid valve 60 is located between the right atrium 22 and the right ventricle 24. The pulmonary valve 62 is located between the right ventricle 24 and the pulmonary artery 26. These two valves direct de-oxygenated blood coming from the body, through the right side of the heart, into the pulmonary artery 26 for distribution to the lungs, where it again becomes re-oxygenated and distributed to the mitral valve 20 and the aortic valve 18.
All of the heart valves are complex structures. Each valve consists of moveable “leaflets” that are designed to open and close. The mitral valve has two leaflets and the tricuspid valve has three. The aortic and pulmonary valves have leaflets that are more aptly termed “cusps” and are shaped somewhat like a half-moon. The aortic and pulmonary valves each have three cusps.
Blood flows into the left ventricle 14 through the mitral valve 20 that opens during diastole. Once the left ventricular cavity has filled, the left ventricle 14 contracts during systole. The mitral valve 20 closes (the leaflets of the mitral valve 20 re-approximate) while the aortic valve 18 opens during systole allowing the oxygenated blood to be ejected from the left ventricle 14 into the aorta 16. A normal mitral valve allows blood to flow into the left ventricle and does not allow leaking or regurgitating back into the left atrium and then into the lungs during systole. The aortic valve allows blood to flow into the aorta and does not allow leaking (or regurgitating) back into the left ventricle. The tricuspid valve 60 functions similarly to the mitral valve to allow deoxygenated blood to flow into the right ventricle 24. The pulmonary valve 62 functions in the same manner as the aortic valve 18 in response to relaxation and contraction of the right ventricle 24 in moving de-oxygenated blood into the pulmonary artery and thence to the lungs for re-oxygenation.
With relaxation and expansion of the ventricles (diastole), the mitral and tricuspid valves open, while the aortic and pulmonary valves close. When the ventricles contract (systole), the mitral and tricuspid valves close and the aortic and pulmonary valves open. In this manner, blood is propelled through both sides of the heart.
The anatomy of the heart and the structure and terminology of heart valves are described and illustrated in detail in numerous reference works on anatomy and cardiac surgery, including standard texts such as Surgery of the Chest (Sabiston and Spencer, eds., Saunders Publ., Philadelphia) and Cardiac Surgery by Kirklin and Barrett-Boyes.
In chronic heart failure (CHF), the size of the heart becomes enlarged. This enlargement can cause the annular size of the valves that separate the atria from the ventricles to also become enlarged. The mitral valve is generally the most affected and has the most serious effects on patient health. FIG. 1B illustrates a sectional view of the positions of the cardiac valves such as the mitral valve 20 present in the heart 10. The annular enlargements can become so pronounced that the leaflets of the valve(s) are unable to effectively close. The annular enlargement most profoundly affects the posterior leaflet 25 of the mitral valve 20. FIG. 1C illustrates a sectional view of the expansion of the annulus 28 of the mitral valve 20. As shown, the annulus 28 expands from a cross-sectional size indicated by the number 21 to the expanded cross-sectional size indicated by the number 23. The expansion/enlargement typically affects the posterior leaflet 25 of the mitral valve 20. During systole, due to the annular enlargement, the valve leaflets do not meet (valve not fully closed, no coaptation), thus some amount of blood flows the wrong way back through the valve from the ventricle and back into the atrium (valve regurgitation) where it raises the pressure in the atrium. This is termed “Mitral Valve Regurgitation” or MVR. MVR reduces the amount of blood pumped by the heart to the body. This reduction in blood flow can be life threatening, especially in patients that have lost ventricular tissue (i.e. heart attack victims), have contraction synchronization problems and/or other problems that reduce the heart's ability to act as a pump.
Regurgitation is common, and is occurring in about 7% of the population. Mitral valve regurgitation is caused by a number of conditions, including genetic defects, infections, coronary artery disease (CAD), myocardial infarction (MI) or congestive heart failure (CHF). Most cases are mild and if the symptoms are bothersome, they can usually be controlled with drugs.
In more serious cases, the faulty or defective valve can be repaired with a surgical procedure such as an annuloplasty. As illustrated in FIG. 1D, an annuloplasty 30 is a surgical procedure in which a synthetic ring 32 is placed around the valve rim (annulus) 34. Sutures 38 are put into the valve annulus 34 and the synthetic ring 32. This causes proper closing by shrinking the size of the valve opening 36. The synthetic ring 32 also reduces and reshapes the annulus 34 to move the posterior leaflet toward the anterior leaflet. FIG. 1E illustrates another surgical procedure in which a heart valve such as the mitral valve 20 is repaired by reconstruction. First, at step A, a section P2 from the posterior leaflet 40 of the mitral valve 20 is excised. Then, sequentially at steps B, C, D, and E, sections P1 and P3 of the posterior leaflet 40 are sutured together. The reconstruction shrinks the size of the valve opening 36. In some instances, a faulty or defective valve must be surgically replaced with a new valve. Examples of new valves include homograft valves (valves harvested from human cadavers), artificial mitral valves, and mechanical valves.
All of the procedures above are typically major surgical procedures that require the opening of the chest by sternotomy or at best through small incisions in the chest wall, performing a heart lung bypass and stopping the heart beat. While surgical procedures such as those mentioned can successfully reconstruct the valve back to a non-regurgitant state, this problem is often associated with Chronic Heart Failure (CHF) and/or other debilitating diseases and thus, the sufferers of the regurgitant valve are often unable to tolerate the required open heart surgery. In CHF patients, the heart is progressively less able to pump sufficient blood to meet the body's needs, usually due to the continuing enlargement of the left ventricle (and adjacent structures) in response to high blood pressure, high heart rate, ECG conduction/timing problems and/or insults to the ventricular tissue, such as Myocardial Infarct (MI). As the body's cardiac compensatory mechanisms act to maintain blood flow (cardiac output), the increased stress and metabolic impacts cause further cardiac enlargement and other detrimental changes. The onset of mitral valve regurgitation further reduces cardiac output and, thus accelerates the CHF process. Therefore, there is a need for a less invasive and traumatic way to treat mitral valve regurgitation (MVR).